Waterproofing membranes are commonly used in the construction industry for sealing bases, underground surfaces or buildings against water penetration.
State-of-the-art waterproofing membranes are multilayer systems comprising a polymer-based barrier layer as the principal layer to provide watertightness. Typical polymers used in barrier layers include thermoplastics such as plasticized polyvinylchloride (p-PVC) and thermoplastic polyolefins (TPO) or elastomers such as ethylene-propylene diene monomer (EPDM) and crosslinked chlorosulfonated polyethylene (CSPE). One of the drawbacks of polymer-based barrier layers is their poor bonding properties; they typically show low bonding strength to adhesives that are commonly used in the construction industry, such as epoxy adhesives, polyurethane adhesives, and cementitious compositions. Therefore, a contact layer, for example, a fleece backing, is typically used to provide sufficient bonding of the polymer-based barrier layer and the structure to be waterproofed.
One of the main challenges related to the multilayer waterproofing membranes is to ensure watertightness after infiltration in case of leak in the barrier layer. Watertightness after infiltration means in general that the sealing construction should be able to prevent the infiltrated water from penetrating to the space between the membrane and the waterproofed surface. A leak in the barrier layer can be a result of inward growing tree roots, material failure or tensile or shear forces directed to the membrane. If the watertightness after infiltration is lost, water is able to flow laterally underneath the membrane and to invade the interior of the building structure. In such cases the exact location of the leak in the barrier layer is also difficult to detect.
U.S. Pat. No. 8,793,862B2 describes a waterproofing membrane comprising a barrier layer, a composite layer arranged on one side of the barrier layer and a network of sealant between the barrier layer and the composite layer. The network of sealant is said to limit the size of area affected by penetrating water in case of water leakage in the barrier layer. In waterproofing applications the membrane is applied on a subsurface in such way that the barrier layer is directed against a concrete base and the composite layer is facing the concrete casted against the membrane. During the hardening process, the composite layer is penetrated by the liquid concrete forming a good bond with the hardened concrete.
US2015/0231863A1 discloses a waterproofing membrane including a barrier layer and a functional layer including a thermoplastic polymer that changes consistency under influence of highly alkaline media and an adhesive. Once the functional layer gets into contact with liquid concrete, the thermoplastic polymer dissolves and allows the adhesive to bond to the cast concrete. The functional layer may additionally comprise other thermoplastic polymers, fillers or concrete constituents. The construction of the functional layer is said to enable working with membranes in adverse weather conditions without diminishing the adhesive capacity of the membrane.
One disadvantage of state-of-the-art multilayer waterproofing membranes is related to the use of adhesives, which increases the complexity of the membrane build-up and consequently the production costs of such membranes. The adhesive has to provide good binding to the low surface energy polymers in the barrier layers, form a strong bond to the contact layer and to fresh concrete and have a good resistance to varying temperature ranges, UV irradiation and oxidation. Adhesives fulfilling all the requirements, if available at all, are expensive and thus increase the production cost of such membranes by a significant amount.
Another disadvantage of state-of-the-art multilayer waterproofing membranes is related to the use of fleece backings as contact layer to provide sufficient bonding between the membrane and the substrate to be waterproofed. In waterproofing and roofing applications the adjacent membrane sheets have to be homogenously joined to each other in a reliable way to ensure watertightness of the sealing construction. Membranes having a fleece backing cannot be joined by heat welding but instead the edges of the membranes have to be bonded together either with an adhesive or with a sealing tape adhered on top of the seam and/or under the seam. The use of an adhesive or a sealing tape to join adjacent membrane sheets complicates the installation process and increases application costs.